Push mower or chainsaw cylinder / piston refresh

How common is it for a small engine to lose compression due to cylinder or piston / ring wear? I have a mower that's 13 years old with 60 psi compression and during a leakdown test I can hear air escaping the oil dipstick. I replaced the head gasket (blown at the time) and noticed some shine in a vertical pattern (direction of piston travel) on the cylinder wall. No groove that I can feel and no other visible damage. The valves are adjusted to spec. The mower is down on power and difficult to start when warm.

A new piston and rings is about $140. Does anybody have experience doing this? Worth it? Simple enough for a shade tree mechanic?

 

That must be a damn nice push mower to spend $140 + your labor on

 

I just did this over the weekend on a Stihl MS362C chain saw, the owner stripped the plug threads and must be a tree came down on the saw as 4 cooling fins were broke. I bought the head/piston kit and some other peripheral parts that needed changing also. It's pretty easy to do if you have mechanical skills.

 

Also a perfect opportunity to hop up your saw

 

$1500 Toro Timemaster

 

One thing to note that is often overlooked with chain saws, is proper warm up time. Everything needs to warm up properly on them before going hog on a log or you get uneven wear on a the cylinder walls leading to premature engine failure. Other small engines like lawn mowers need this as well.

 

Too bad all these cheap push mowers don't even have a throttle or a choke or even an oil drain plug. All plastic carbs, unbelievable how much they've cheapened shit up.

 

Down on power & hard to start when warm:

If its kicking back on you when you pull the rope, check if the flywheel key is broken and your timing is off.

 

I may have run the engine low on oil, and I did not change the oil until recently. Sooo, the engine might be a little abused.

I don't think I will go so far as to replace the cylinder assembly, maybe just the piston rings with a light hone of the cylinder walls. Or should I replace the piston as well? What grit hone should I use, I'm thinking 400 since 220 might be too aggressive? Don't know.

 

Why not do it? If nothing else it might be fun. Especially since there's nothing you're gonna buy that's as good for anywhere near $1500 much less the $150.

Plus when you're zooming on the hotties they'll really dig that you rebuilt your lawn mower by yourself.

 

I did abuse my chainsaw as well with too little warm up and too little cool down, and not keeping the chain sharp so more work on the saw. I'm learning and hope that I've learned before I did permanent damage to my engines.

 

Should I replace the piston pin and con rod? Probably just the piston pin right? Or just re-use the old one?

 

This happened on the 4wheeler at deer camp and took a lot of cussing til we figured it out

Runs better than new now with that and proper valve lash.

If he can hear air in the dipstick tube it's probably ring/cylinder

Also, electric chainsaw owner here....fkn love that thing.

Old husky did a clutch meltdown and it just made sense.

 

In light of this new info I'd say you're wasting your time and money doing those things as you may have fubar'd other parts of the engine that like oil

 

Got myself one of the M18 Fuel 16" Milwaukee chainsaws myself. So handy to have for cutting medium wood around the place and it rips!

Still hit the gas when doing a big days cut after taking the tree down though.

 

I say send it. The lack of good quality oil is going to have affected the rings far more than the rotating assemblies.

 

Price it out. If it makes sense, while you have it apart, I say do it. We rebuilt mowers in shop class in high school. Easy stuff. Don’t go cheap on Amazon with parts. Get OE if possible.

 

Scag 30, buy once cry once. Time master will cost the same if not more after constantly repairing it.

 

I just had to source a turbo speed sensor for a cummins off of Amazon because cummins themselves couldn't get it...and couldn't even get me a date for the backorder.

Prime had it on my doorstep 2days later

What a time to be alive

 

I ordered a carb off eBay for a Stihl chainsaw, spent the extra to get a genuine Stihl. Came in Stihl packaging, opened it up, made in China.